Monday, January 20, 2014

A paper published today in The Holocene reconstructs temperatures of the Gulf of Alaska over the past 1200 years and finds another non-hockey-stick with "a warm interval centered on AD 950 for coastal Alaska that occurs around the time of the ‘Medieval Warm Period’, a warming that is only rivaled by recent decades." The paper adds to over 1,000 peer-reviewed publications finding the Medieval Warm Period was global and as warm or warmer than the present.

In addition, the authors find the climate over the past 1200 years was driven by long and short-term solar and lunar tidal cycles, finding, "Spectral analysis of this reconstruction supports the centennial pacing identified as a 170–220-year cadence consistent with solar variability [the de Vries solar cycle]. On the decadal to bidecadal scale, the reconstruction reveals ~10- and 18-year cycles, which have been observed elsewhere in climate records for western North America and are linked to solar and lunar tidal forcing, respectively. " "This tree-ring reconstruction supports centennial modes of solar forcing as a driver of surface air temperatures in the Gulf of Alaska, with lunar tidal, solar variability, internal variability, and volcanism, impacting climate on annual to decadal timescales."A similar reconstruction from the Gulf of Alaska over the past 500 years [which does not include the Medieval Warm Period 1000 years ago] shows there is nothing unusual, unprecedented, or unnatural regarding Alaskan temperatures over the past 500 years. The paper finds reconstructed temperatures were higher during the 1920's-1930's than at the end of the record in the year 2000.

Other temperature reconstructions from Alaska also show the 1920's - 1930's were warmer than at the end of the record in 2000, including the 3 below:

Abstract

A 1200-year-long tree-ring width record from living and subfossil mountain hemlock wood is used to reconstruct February through August temperatures for the Gulf of Alaska, providing a record of past climate variability for the Northeast Pacific sector that captures interannual to centennial timescales. The moderate elevation at the tree-ring sites has allowed these trees to retain their temperature signal without evidence of the so-called divergence effect, or underestimation of tree-ring inferred temperature trends, which is observed at many northern latitude forest locations. This ‘divergence-free’ reconstruction reveals centennial trends that include a warm interval centered on AD 950 for coastal Alaska that occurs around the time of the ‘Medieval Warm Period’, a warming that is only rivaled by recent decades. Spectral analysis of this reconstruction supports the centennial pacing identified as a 170–220-year cadence consistent with solar variability. On the decadal to bidecadal scale, the reconstruction reveals ~10- and 18-year cycles, which have been observed elsewhere in climate records for western North America and are linked to solar and lunar tidal forcing, respectively. Temperature minima that occur at AD 969–970 and 1698–1700 correspond with the timing of major volcanic events. This tree-ring reconstruction supports centennial modes of solar forcing as a driver of surface air temperatures in the Gulf of Alaska, with lunar tidal, solar variability, internal variability, and volcanism, impacting climate on annual to decadal timescales.